Redox Chemistry of Mn2+ on N‐Doped Porous Carbon Fibers for High‐Performance Electrochemical Energy Storage

Abstract

Earth‐abundant manganese (Mn) compounds have multifarious valence states that make Mn advantageous for electrochemical energy storage applications. Benefiting from the unity of opposites in redox chemistry, a novel aqueous all‐Mn energy storage device (AMESD) based on the redox chemistry of Mn2+ is proposed, which is a simple‐structured battery that can be initially assembled by two bare carbon fiber cloths (CFCs) and the electrolyte. Moreover, the effects of electrolyte optimization and the modification of CFCs on the energy storage performance of the novel battery are discussed. The device based on N‐doped porous CFCs achieves the highest areal capacity of 1.46 mAh cm−2 (≈152.1 mAh g−1), along with an energy density of 1.10 mWh cm−2 and a power density of 9.66 mW cm−2. More impressively, the charge–discharge cycles at a capacity of 0.33 mWh cm−2 are performed 40 000 times and it can maintain a high‐capacity retention rate of 93.5%. Even at a low current of 1 mA cm−2, the capacity retention rate after 100 cycles is maintained to 86%. Herein, a new option for low‐cost, ultrastable aqueous battery design is provided and the possibility of Mn‐based anodes for energy storage applications is explored.